Enriched subpopulations of cells from a heterogeneous population of cells are often required for many clinical and research applications. Many subpopulations of cells exist in bodily fluids, including blood. Isolating and examining subpopulations of cells from blood is an attractive option due to the minimally-invasive nature of a venous puncture. Examples of useful cell subpopulations found in the blood can include circulating tumor cells (CTCs), cancer stem cells (CSCs), hematopoietic stem cells (HSCs), and endothelial progenitor cells (EPCs). CTCs and CSCs are of high research and commercial interest due to their critical role during cancer progression, and their potential as a diagnostic and prognostic indicator of patient response to treatment (Cristofanilli et al., J. Clin. Onc., 23(7): 1420-1430, 2005). In addition to their clinical utility, these cancer cells are an important biological source for targeted drug development and discovery of novel biomarkers (De Mattos-Arruda et al., Clin. Colorectal Can, 10(4): 279-289, 2011; Generali et al, J Natl Cancer Inst Monogr 2011(43): 67-70, 2011; Kelloff and Sigman, Nature Rev Drug Disc 11(3): 201-214, 2012; Wicha and Hays J Clin Onc 29(12): 1508-1511, 2011). HSCs are rare cells that have the capacity to provide complete restoration of all blood cell lineages after bone marrow ablation and are considered ideal targets for various clinical applications including stem cell transplantation and gene therapy (Ng et al., Methods Mol Bio, 506:13-21, 2009). EPCs are a circulating cell population that can be derived from bone marrow and have important regeneration properties.
Recent developments in the life sciences have made it increasingly more important to be able to rapidly and efficiently isolate, characterize, and enrich cell subpopulations from a heterogeneous population without compromising the integrity of the cells. However, a critical problem for the field has been an inability to capture and enrich rare target cell subpopulations in sufficient quantities to conduct meaningful research. The current detection methods for isolating target cell subpopulations often rely on the use of antibodies, ingestion of a matrix, or complex microfluidic devices that have led to inconsistent findings and limited sample (Diamandis et al. Clin Chem 57(11): 1478-1484, 2011). Therefore, there exists a need for methods to capture, detect, enrich, and use cell subpopulations for clinical, therapeutic, diagnostic, and research applications.